This invention relates generally to infrared vidicon television camera tubes and more specifically to a solid state retina structure used as a sensing layer in such tubes.
Advances in the art of infrared detection have created increasingly sophisticated and costly equipment. Some of the aforesaid equipment, while capable of achieving superlative results in the laboratory has lacked utility in the field.
The original infrared image converter tube was of simple design and consisted of a photocathode capable of emitting electrons, a phosphor screen and an electron lens system for focusing the emitted electrons on the screen. The wavelength range to which the tube is sensitive depended upon the spectral response of the photocathode. Subsequent devices utilized rare and hard to produce compounds combined with moving optics. Deficiencies in the prior art were cured to some extent, however new problems were created by way of short operational lifetime, difficulty in uniformity in the manufacturing process and a high cost factor.
Recent advances in the art have shown that solid state systems are capable of providing more and better information in a much more reliable manner than any prior known devices. Infrared sensing systems employing an array of solid state detectors such as the Schottky barrier diode fulfill most requirements for infrared detection in the spectral band from 1 micrometer to 6 micrometers in wavelength. These devices, however, when utilized in an infrared vidicon television camera tube have required a high velocity electron gun. The high velocity electrons charge the metal electrodes positive by operating at landing voltages above the secondary emission cross-over point. The use of a high velocity read-out required complex tubes which are expensive, difficult to control and subject to excess noise mechanisms which degrade imagery. The apparatus and system to be described uses conventional low velocity electron gun to place a negative charge on the substrate, thereby eliminating the requirement for high velocity operation, simplifying the camera, lowering costs and improving reliability.